Method and apparatus for the measurement of dye dilution in blood

ABSTRACT

A method for determining cardiac volume parameters wherein a test dye is added to blood and a photometric measurement of the light absorption of dyed blood is carried out by an electrooptical system which includes a photosensitive means to determine dye dilution in the blood.

United States Patent Dorsch July 18, 1972 METHOD AND APPARATUS FOR THEferences Cited MEASUREMENT OF DYE DILUTION IN UNITED STATES PATENTSBLOOD 3,008,370 1 H196] v Uribe ..356/40 [72] Inventor: Johannes Dorsch,Schonhausenstrasse 11, 3,066,570 12/1962 Goodman BI --.--356/41 vBremen, Germany 3,296,922 1/1967 Goldberg ..356/40 [22] Filed: June 221970 3,437,822 4/1969 Fitzsimmons ..356/40 X Primary Examiner-Ronald L.Wibert 21 L 43,194 Assistant Examiner-Orville B. Chew, lI

Attorney-Wolf, Greenfield and Sacks Related US. Application Data [63]Continuation of Ser. No. 416,863, Dec. 8, 1964, aban- [57] ABSTRACTdoned- A method for determining cardiac volume parameters wherein a testdye is added to blood and a photometric mea- [52] US. Cl ..356/40suremem f the light absorption of dyed blood is carried out [51] Int.Cl- ..G0ln 33/16 by an electro optica l system which includes aphotosensitive [58] Fleld of Search ..356/ 39, 40, 41; 250/218 means todetermine dye dilution in the blood 2 Claims, 10 Drawing FiguresPatented July 18, 1972 3,677,648

4 Sheets-Sheet 1 HETHYLENE CARDIO- BLLlE\ /GREEN Patented July 18, 1972Patented July 18, 1972 3,677,648

4 Sheets-Sheet 5 fa m p [e Carzfairlefl Patented July 18, 1972 4Sheds-Sheet 4 HbU METHOD AND APPARATUS FOR THE MEASUREMENT OF DYEDILUTION IN BLOOD RELATED APPLICATION This application is a continuationof copending U.S. Pat. application Ser. No. 416,863 filed Dec. 8, 1964and now abandoned.

BACKGROUND OF THE INVENTION Light absorption or extinction (logarithm oflight absorption) is dependent not only on concentration of test dye butalso on several influences disturbing the measurement of test dyeconcentration, as for example O -saturation, concentration C of thenatural color components haemoglobin Rb and oxyhaemoglobin HbO,,thickness D of the sample used for measurement (when using the human earfor instance) and is dependent on the velocity of flow of blood throughthe test region.

The I-Iband HbO -curves of FIG. 2 of the accompanying drawingsrepresenting the extinction dependency of blood (without test dye) withand 100 percent O -saturation respectively are crossing one another atthe so-called isosbestic point at the wavelengths k 805 mu. At thispoint extinction is independent of 0 -saturation. It is known tocompensate the other four influences by forming the difference ofextinctions at two different wavelengths while simultaneous maintainingthe 0 -saturation at a known constant value. How ever, to maintain 0'-saturation at a known constant value during measurement, is mostdifficult.

SUMMARY OF THE INVENTION wavelengths then equalizing and nullifying saidfirst and second isosbestic extinction values, so that after adding atest dye, absorption values of which are different at the wavelengthsbelonging to said two isosbestic values, extinction values are dependentonly on fluctuations of test dye concentration and independent onfluctuations of 0 -saturation, concentration C of the natural colorcomponents, thickness D and velocity of flow of blood.

DETAILED DESCRIPTION OF THE INVENTION For a better understanding of thepresent invention, reference will now be made to the accompanyingdrawings, in which:

FIG. 1 is a graph showing extinction values and wavelengths, for sixknown dyes;

FIG. 2 is a graph showing the extinction relationships of reducedhaemoglobin and oxidized haemoglobin, illustrating a first embodiment ofthe new method;

FIGS. 3a, 3b and 3c are a diagram showing extinctions for variouswavelengths, further illustrating said first embodiment;

FIG. 4 is a graph like FIG. 2, illustrating a second embodiment of thenew method;

FIGS. 5a, 5b and 5c are a diagram like FIG. 3, further illustrating saidsecond embodiment; and

FIG. 6 diagrammatically illustrates an apparatus for continuousmeasurement of blood in respect of three different color wavelengths;whereby the left and middle part is illustrating the apparatus for thefirst embodiment according to FIGS. 2 and 3 and the left and right partis illustrating the apparatus for the second embodiment according toFIGS. 4 and 5.

For determining cardiac volume parameters by injection of a test dyeinto blood and photometric measurement of the light absorption of thedyed blood at chosen regions, two dye groups are hitherto customary; theblue dyes, the absorption maxima of which lie between A 600 and 660 mu,and the so called green dyes, the absorption maxima of which lie atabout k 800 mu, but which extend deep into the short-wave red region.The absorption curves of these and other dyes are shown in FIG. 1 of theaccompanying drawings.

In the photometric measurement of light absorption in blood, a so calledextinction value, is used, in order to lead to a linear representationof the dye concentration in the blood. The extinction value as known inthe art is the logarithm of the absorption or the logarithm of decreaseof light intensity. These extinction values, however, are normally notonly dependent on the added test dye but are influenced in combinationby the disturbing extinctions underlying fluctuations from change of l.0 -saturation,

2. concentration C of I-Ib and Hb0,, 3. thickness D of the sample,

4. velocity of flow of blood.

RE 1 With Hb in the blood the extinction (without test dye added) wouldfollow the dotted curve Hb in FIG. 2. For a fixed concentration C of Hbin the blood, fixed thickness D of test sample and fixed flow effect,therefore, the curve I-Ib in such a case would be used as a zero linefor the measurement of the extinction by the test dye after addition ofsuch test dye.

RE 2: Would only Hb0 be present in the blood then with the same threeconditions as are pointed out above in connection with Hb as colorcomponent, the extinction would follow the curve Hb0 in FIG. 2 and thenthis curve would be a zero line for measurement of extinction by testdye added to the blood.

RE 3: Overmore the extinction is dependent on the concentration C ofsaid two natural color components Hb and Hb0 so that all values of saidcurves will increase or decrease in a proportional degree.

RE 4: The extinction is dependent on the thickness D of the sample usedfor measurement. When using a cuvette the thickness is constant. Whenusing the human body, for instance the human ear, the thickness will besubjected to alterations. Alterations of the thickness D will cause aproportional shifting of the curves Hb and Hb0 The compensation ofinfluences of fluctuations of thickness D is of greatest significanceespecially in connection with measurements through the blood filledtissue of the ear, in order to suppress the influence of pulsations onthe measuring result.

RE 5: The extinction is also dependent on the velocity of flow of bloodthrough the sample or test region. The erythrocytes which contain theblood color haemoglobin are disklike bodies which will orientate intostreamline to a degree dependent on the velocity of flow. Thisorientation will cause a change of extinction which phenomenon is calledflow effect.

It is an object of the present invention to provide a measuring methodwhich enables to compensate influences of fluctuations of concentrationC, thickness D and flow effect also in the case of varying O-saturation. Hitherto, it was not possible simultaneously to compensatefluctuations of 0 -saturation' and said other fluctuations of influencesof natural color of the blood, and thereby exclude them as a source ofdisturbance in test color measurements, since the light wave range whichwas usable in practice only gaveone isosbestic point. Attempts havealready been made in connection with green dye measurement, tocompensate said three other influences by addition of a wavelengthbeyond 900 m ,u., at which the green dyes no longer had any lightabsorption, but: in this case a sensitivity to 0 -saturation occurred.Now by the present invention it is possible to overcome all said fourdisturbances of extinction, that is to make the measurement of test dyeextinction independent of said four disturbances.

At first let us examine the disturbances by the natural color componentsI-Ib and l-Ib0 In practice is is not possible to use the curve Hb or Hbas zero line, because blood in the human body has a 0 -saturationbetween zero (hb) and 100 (l-Ib0 Only in one point, the cross point,named natural isosbestic point of the two curves Hb and Hb0 theextinction is independent on (l -saturation. Therefore, it is possibleto make a measurement at A 805 mu. After adding the test dye theextinction value a, will change and the value of increase of extinctionat A will give a true value of extinction by the test dye if theinfluences according to the above numbers 2, 3 and 4 are neglected,because alterations of 0 -saturation do not influence the value ofextinction a in the natural isosbestic point, because in this point I-Iband I-IbO, have always the same extinction value a,,. Thus, in order tobe independent of fluctuations of 0 -saturation it is customary to usethe extinction values of a test dye at the natural isosbestic point A805 my" This, of course, is possible in connection only with test dyesof good sensibility at A as e.g., cardio-green. This measurement formshitherto the selected method of measurement especially with patientshaving high fluctuations of 0 -saturation.

The present invention is based upon the consideration that, if we wouldhave two natural isosbestic points, we could use the measurements inthese two points for compensation of said three other disturbinginfluences according to the above numbers 2, 3 and 4. However, such twonatural different isosbestic points are not available. Therefore,according to the invention there is proposed a method to form one or twoartificial isosbestic values with the same characteristics as has theextinction value at the natural isosbestic point.

a. example for methylene-blue dye; FIGS. 2, 3

FIG. 2 is illustrating the establishment of such an artificialisosbestic value which may be used in connection with the test dyemethylene-blue. To obtain an artificial isosbestic value two A-values A,and A are chosen. Preferably these two points are chosen in such a waythat one of the two wavelengths, in the example the wavelength A, willgive a high extinction value for the test dye methylene-blue, whereasthe other wavelength A, will give no or a much more lower extinction forthe test dye.

The three vertical lines in FIG. 2 indicate the extinction values atthree wavelengths which are especially suited for performing the methodof the present invention, in connection with methylene-blue as thetesting dye.

At A, 660 mu, methylene-blue has its absorption maximum. However, at A760 my. and A 805 mu, the isosbestic point, it no longer has anysignificant light absorption.

In the curves of the extinction values for Hb0 and Hb according to FIG.2, a, represents the extinction of Hb0 and a, b, represents theextinction of I-lb at A, 660 mg. The cor responding extinctions for A760 mp. are designated by 0 and b Possible alterations of 0 -saturationfrom 0 to 100 percent take place on the portions b', and b The portionindicated by a for A 805 mp. at the natural isosbestic point P is thesame for I-Ib and I-Ib0 For further explanation, the portions a,, b, anda and b for A, 660 and A, 760 my in FIG. 2 are combined for graphicalevaluation as vertical lines, in the form shown in FIG. 3 I. The baseline represents zero extinction. If the total extinctions a, b, and a b,for A, 660 mp. and A 760 mp. are subtracted from each other, then adifferent value is produced for each 0 -saturation level. The same istrue for a C- and D-alteration, which leads to a proportionalenlargement or reduction of the portions.

With o -saturations ofx 0 percent, 50 percent or 100 percent forinstance the extinctions at A, and A are as is indicated in the threedotted lines of FIG. 1 I: atA,:a,+b, -x(=0, l orO, 5) filters F F Fbased on the wavelengths A 900, A 990 and A 805 m are arranged. Therequired monochromatic action can be increased by selection ofphotocells P,, P P or P P P with suitable sensitivity spectra. The threeextinction actions which are obtained in this way and which arecontrollable in their degree, may be so co-ordinated by means of aselection switch means, that from any two systems the total value or thedifference value of the extinctions can be formed. Such a differencevalue then allows a difference formation to be effected in relation tothe remaining third extinction value a at A 805 my" If this differenceis brought to zero in the measuring device, then it does not change byfluctuations of 0,-saturations and also not by fluctuations of C and Dand fluctuations of flow effect and will depend only on theconcentration of added test dye.

For the first example, the combination a b shown in FIG. 6 applies, andfor the second example the combination a 0 applies.

For further explanation, the portions a,, b,, x'b, and a b,, x b, for A,660 mp. and A, 760 my in FIG. 2 are combined for graphical evaluation asvertical lines, in the form shown in FIG. 3 I. The values a, x b, and a,x ab, are available at the outputs of photocells P,, P, in FIG. 6. Thebase line represents zero extinction. If the total extinctions a, x b,and a +x b,. for A, 660 my and A 760 mp. would be subtracted from eachother, then a different value would remain for each 0 -saturation level.The same is true for a C- and D-alterations, which lead to proportionalenlargements or reductions of the portions, which could be expressed bymultiplying by a factor k the extinction values k(a, x b,) and k(a,. x bBecause this factor will change both portions of all the extinctionvalues to the same degree, it can be set k l in the following discussionof compensation of fluctuations of 0 saturation.

The values a, x b, and a x b, are effective before the test dyemethylene-blue is added to the blood. After addition of the test dye theextinction value A, will increase by a portion, whereas the extinctionat A will remain unchanged because the extinction value of the test dyemethylene-blue at A is approximately zero.

The influence of unknown 0 -saturation of x percent is compensated bythe following steps:

a. the extinction value a: b x at A is multiplied by b,/b

within a multiplier or amplifier V (FIG. 6), so that at the outputs ofamplifiers V,, and extinction values (a, +2: b,) and [(a 1)/b x b,] areobtained, in which the second portions are equalized to be both x b,(compare FIG. 3 II).

b. forming the difference from said output values: (a, x b,) [(a,r)/b,,b+x b,] a, a, b,/b This value is independent on 0 -saturation xand only is dependent on C, D and flow effect. Therefore, thisextinction value just as the extinction value a at the naturalisosbestic point A, 805 mg is independent on changes of 0 -saturation xand therefore is named artificial isosbestic value in the sense of thepresent invention.

c. Compensation not only of alterations of (l -saturation but also ofinfluences or changes of C and D and of flow effect, will be explainednow.

For compensation of influences of C and D and of flow effect to theextinction value the extinction value a at A is multiplied by a factor R(i.e., l, 45) within multiplier L which factor R is chosen in such amanner that the absolute value of the above artificial isosbestic valuela, a- MM is equal to the absolute value of IR 00]. Therefore, byforming the sum of that two values a b, (12 -al) R a we obtain afterinsertion of the test dye a compensated extinction value whichessentially is independent on o -saturation as well as on concentrationC, of the natural blood colors, thickness D and flow effect and onlydepends upon the concentration of the inserted test dye. From FIG. 2 itmay be seen that it is not possible to use the test dye methylene-blueat the natural isosbestic point A because the extinction value ofmethyleneblue at A is zero. Therefore, the above method for forming oneor more artificial isosbestic points not only gives the possibility ofsimultaneous compensating 0 -saturation fluctuations and the other threedisturbances as will be explained more detailed in the followingdiscussion, but quite apart therefrom gives the advantage that inperforming the test dye measurement it is no longer necessary to use thenatural isosbestic point at the wavelength A As a result test dyes canbe used which are unsuitable for the natural isosbestic point likemethylene-blue.

b. Example for cardio-green, FIG. 4, 5.

A second example will be given for explaining the application of thethree color compensation principle with use of the test dye known ascardio-green (indocyanine green). Hitherto, this dye has been measuredonly at A 805 m;;., that is to say so as to be independent of 0-saturation. Recently, a two wave compensation arrangement has beenproposed by the Waters Corporation in which for compensation of the floweffect, in addition to the dye measurement wavelengths A 805 mp, alonger compensation wavelength which is independent of the test dye isused. However, a certain degree of dependence on 0 -saturation comesinto the measurement. The principle of the invention allows this to beeliminated.

In FIG. 4, the spectra of I-Ib and Hbo are indicated by three verticalsections at )t 805, A 900 and A, 990 mu which represent the extinctionsand total extinctions of l-Ib and l-lb0 They are separately shown asvertical portions in FIG. I.

Just as in the first example the portions 2: b and x b are equalized bymultiplying x b within amplifier V by the factor b /b (FIG. 5 II). Thenthe artificial isosbestic value is formed by forming the difference ofoutputs of V and V and the sum or difference of this artificialisosbestic value and the natural isosbestic value a is formed afterhaving equalized these two isosbestic values by multiplying the naturalisosbestic value 11 by an equalizing factor f.

This allows a continuous test color measurement for cardiogreen which isindependent of 0 -saturation and of C- and D- alterations and floweffect. For measurement by means of the ear, the same considerations aretrue, but a further extinction for the light absorption of the tissuehasto be added to all total extinctions, the tissue acting practicallyas a grey filter which does not change during the measurement.

For the first example, the combination [1 shown in FIG. 6 applies, andfor the second example the combination III applies.

Many alterations and other embodiments are possible within the scope ofthe invention. More particularly, the provision of an artificialisosbestic value also has independent significance whether or not a C-and D-compensation is to be obtained by use of two isosbestic values.The compensation for forming an artificial isosbestic value can beachieved also by proportional formation instead of by difference or sumformation.

I claim:

I. A method for determining cardiac volume parameters wherein a test dyeis added to blood and a photometric measurement of the light absorptionof dyed blood is carried out by an electro-optical system which includesa photosensitive means to determine dye dilution in the blood, saidmethod comprising the steps of,

a. measuring the light absorption values of the blood without any dyeadded at a first wavelength,

b. measuring the light absorption values of the blood without any dyeadded at a second wavelength,

c. operating said electro-optical system to obtain modified lightabsorption values by equalizing the 0 -saturation-dependent portions ofsaid light absorption values at said first and second wavelengths bymultiplying the light absorption value at said second wavelength by afactor equal to the 0 -saturation-dependent portion at the minimum of 0-saturation at said first wavelength divided by the O-Saturation-dependent portion at the minimum of 0 -saturation at saidsecond wavelength,

d. subtracting said modified light absorption value at said secondwavelength from said light absorption at said first wavelength, thedifference value thus being independent of 0 -saturation to establish afirst artificial isosbestic value,

c. deriving a second artificial isosbestic value by the same steps asset forth in steps (a) to (d) using absorption measurement at twowavelengths different from said first and second wavelengths,

f. operating said electro-optical system to equalize said firstartificial isosbestic value independent of 0 -saturati0n and said secondartificial isosbestic value independent of 0 -saturation,

g. forming a compensated difference value which is the differencebetween said first artificial isosbestic value and said secondartificial isosbestic value and this compensated difference value beingzero' before adding test dye and independent of 0 -saturation,concentration, layer thickness and flow effect,

h. adding a test dye to the blood the absorption values of which at saidfirst and second wavelengths are different from the absorption values atsaid two other wavelengths and then,

i. determining the light absorption values of the dyed blood bymeasuring the variations of said compensated difference value (understep (g)).

2. A method for determining cardiac volume parameters wherein a test dyeis added to blood and a photometric measurement of the light absorptionof the dyed blood is carried out by an electro-optical system whichincludes a photosensitive means to determine dye dilution in the blood,said method comprising the steps of,

a. measuring the light absorption values of the blood without any dyeadded at a first wavelength,

b. measuring the light absorption values of the blood without any dyeadded at a second wavelength,

. operating said electro-optical system to obtain modified lightabsorption values by equalizing the 0 -saturation-dependent portions ofsaid light absorption values at said first and second wavelengths bymultiplying the light absorption value at said second wavelength by afactor equal to the 0 -saturation-dependent portion at the minimum of 0-saturation at said first wavelength divided by the O-saturatiQn-dependent portion at the minimum of 0 -saturation at saidsecond wavelength,

. subtracting said modified light absorption value at said secondwavelength from said light absorption at said first wavelength, thedifference value thus being independent of 0 -saturation to establish afirst artificial isosbestic value,

. deriving a second isosbestic value by measuring the light absorptionvalues of the blood at the wavelength of the natural isosbestic point ofthe blood (A 805),

f. operating said electro-optical system to equalize said firstartificial isosbestic value independent of 0,-saturation and said secondisosbestic value independent of 0 -saturation,

g. forming a compensated difference value which is the differencebetween said first artificial isosbestic value and said secondisosbestic value and this compensated difference value being zero beforeadding test dye and independent of 0 -saturation, concentration, layerthickness and flow effect,

h. adding a test dye to the blood the absorption values of which at saidfirst and second wavelengths are different from the absorption values atsaid two other wavelengths and then,

i. determining the light absorption values of the dyed blood bymeasuring the variations of said compensated difference value (understep (g)).

2. A method for determining cardiac volume parameters wherein a test dyeis added to blood and a photometric measurement of the light absorptionof the dyed blood is carried out by an electro-optical system whichincludes a photosensitive means to determine dye dilution in the blood,said method comprising the steps of, a. measuring the light absorptionvalues of the blood without any dye added at a first wavelength, b.measuring the light absorption values of the blood without any dye addedat a second wavelength, c. operating said electro-optical system toobtain modified light absorption values by equalizing the02-saturation-dependent portions of said light absorption values at saidfirst and second wavelengths by multiplying the light absorption valueat said second wavelength by a factor equal to the02-saturation-dependent portion at the minimum of 02-saturation at saidfirst wavelength divided by the 02-saturation-dependent portion at theminimum of 02-saturation at said second wavelength, d. subtracting saidmodified light absorption value at said second wavelength from saidlight absorption at said first wavelength, the difference value thusbeing independent of 02-saturation to establish a first artificialisosbestic value, e. deriving a second isosbestic value by measuring thelight absorption values of the blood at the wavelength of the naturalisosbestic point of the blood ( lambda 0 805), f. operating saidelectro-optical system to equalize said first artificial isosbesticvalue independent of 02-saturation and said second isosbestic valueindependent of 02-saturation, g. forming a compensated difference valuewhich is the difference between said first artificial isosbestic valueand said second isosbestic value and this compensated difference valuebeing zero before adding test dye and independent of 02-saturation,concentration, layer thickness and flow effect, h. adding a test dye tothe blood the absorption values of which at said first and secondwavelengths are different from the absorption values at said two otherwavelengths and then, i. determining the light absorption values of thedyed blood by measuring the variations of said compensated differencevalue (under step (g)).